The invention relates to the cooling of electronic components and, in particular, to the cooling of electronic components housed within an electronics cabinet.
The speed of electronic components steadily accelerates and, at the same time, increase in density. Additionally, more components are often placed within a single housing than ever before. All these factors: increased speed of operation, increased density of circuitry within a component, and the increased density of components within a housing, contribute to higher operating temperatures. As the temperature of electronic components increase, their reliability decreases. Heat equals failure and it must be dissipated in order to ensure the proper operation of systems that employ components. Various approaches to the cooling of electronic components have been pursued. Forced fluid cooling is described, for example in, U.S. Pat. No. 4,851,965 issued to Garbuzda et al (Garbuzda), which is hereby incorporated by reference. Garbuzda describes the use of jet impingement of air onto the heat generating component through separate plenums. A circuit pack with inboard jet cooling is described in U.S. Pat. No. 5,067,047 issued to Azar, which is hereby incorporated by reference. It has also been suggested that air can be blown onto the components through holes in the enclosures or shields surrounding the circuit components (see, for example, U.S. Pat. No. 4,393,437 issued to Bell et al and U.S. Pat No. 4,408,255 issued to Adkins, both of which are hereby incorporated by reference. It has been suggested that holes in the circuit boards themselves could allow air to impinge on components in circuit packs which are stacked (see, for example, U.S. Pat. No. 4,399,484 issued to Mayer, which is hereby incorporated by reference).
The cooling of autonomous electronic components, components that are enclosed within a cabinet and that are designed for operation with little human intervention is particularly difficult. Such systems often operate in relatively remote locations and must be extremely reliable. Such autonomous systems are typically exposed to the elements, inasmuch as they are not located within a building of any sort, and, because of their exposure to the elements, they often experience tremendous inflows of heat from their surrounding environment. Coupled with the increasing levels of heat generated by enclosed electronics, and the extreme reliability required for such semi-autonomous operation, the cooling of such systems present a significant challenge.
An electronic cooling system that provides efficient and substantial cooling potential for electronics systems would be highly desirable.
An electronics cooling system in accordance with the principles of the present invention includes an electronics cabinet that is thermally connected with the ground upon which it sits. The cabinet may or may not sit directly on the earth below, but the thermal connection is made with the earth below, and in the near vicinity of, the cabinet, thereby employing the earth as a heat sink. In an illustrative embodiment; an enclosed cabinet includes a heat pipe that makes thermal contact with the ground in the immediate vicinity of the electronics cabinet. Racks for holding electronic printed circuit cards within the cabinet may be made of high thermal conductivity (that is, at least 40 W/mK) materials, such as Aluminum, Copper, or alloyed materials. Such racks may be mounted to a thermally enhanced frame, that is, a frame of high thermal conductivity material, in such a way as to transfer a substantial portion of thermal energy within the rack to the thermally enhanced frame. Additionally, the thermally enhanced frame may be configured to make similar high conductivity contact with a heat pipe.
The heat pipe, in turn, is connected to conduct heat from the inside of the cabinet to the earth below the cabinet. In addition to conductive thermal transfer from the thermally enhanced frame, the heat pipe may include any of a variety of distributions of finned heat exchangers situated within the cabinet to increase the surface area of the heat pipe exposed to the interior environment of the cabinet. To further enhance heat transfer from the enclosed electronics to the heat pipe, one or more fans may be employed to circulate air within the enclosure. The fan may direct a flow of air to ensure that air heated by the enclosed electronics circulates over a heat exchanger that is in thermal contact with, or a part of, the heat pipe.
An electronics cabinet in accordance with the principles of the present invention is particularly suited for use in uncontrolled environments, such as may be encountered by remote telecommunications switches and wireless telecommunications equipment, for example. In such an application, the exterior surfaced of the cabinet may be thermally reflective and the walls of the enclosure may be insulated to maximize the efficiency of the heat pipe""s cooling effects. Additionally, a solar shield may be attached to the exterior of the enclosure to further enhance the effectiveness of the heat pipe. The heat pipe may be distributed in throughout an extensive area beneath the cabinet in order to take further advantage of the thermal mass of the earth.